September 17, 2026 Author : Pedro Beleza (neurology) In people with major depression, cognitive symptoms such as memory and concentration difficulties occur in a high proportion of cases. Difficulty thinking or concentrating is one of the diagnostic criteria for major depressive disorder (DSM-5-TR). This diagnosis requires the presence of at least five out of nine possible symptoms for a minimum of two weeks, with either depressed mood or loss of interest in usual activities being mandatory, present for most of the day and nearly every day. The cognitive domains most affected by depression are: Anterograde memory, that is, the ability to learn and retain new information; Processing speed; Sustained attention; Executive function, including planning, organizing and decision-making. A particularly characteristic feature is negative memory bias . People with depression tend to recall negative events more easily than positive ones. In addition, they often describe past experiences in a vague and general way rather than as specific memories anchored in a precise time and place, a phenomenon known as reduced autobiographical memory specificity . In older adults, depression may give rise to a condition that mimics dementia, classically referred to as pseudodementia . It is distinguished by its more rapid onset and by the person's active and often distressing complaints about their memory. In the long term, depression is associated with an increased risk of cognitive decline and dementia . From a biological perspective, the link between depression and cognitive impairment is mainly related to excess cortisol, the body's primary stress hormone, resulting from dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis. The hippocampus, a brain structure that plays a central role in the formation of new memories, is particularly sensitive to cortisol. Prolonged exposure to high levels of this hormone is associated with a reduction in hippocampal volume, visible on brain imaging studies, a process that is largely reversible when cortisol levels return to normal with treatment. Treatment of depression generally improves cognitive symptoms, but often not completely : more than 70% of patients retain some degree of residual cognitive impairment even after remission of depressive symptoms. Clinical follow-up should therefore pay specific attention to these symptoms and not focus solely on mood. Cognitive deficits that fail to improve despite appropriate treatment, or that worsen over time, should raise suspicion of an underlying dementia. Regular physical exercise and cognitive rehabilitation are complementary interventions with demonstrated benefits and should be considered an integral part of the treatment plan. Meet the neurology clinical team from Hospital da Luz network. The content published in the Health Guide is intended for the general public and is provided for informational and educational purposes only. It does not replace individual medical assessment, diagnosis, or personalized clinical advice from a qualified healthcare professional. The content is produced or reviewed by physicians and other healthcare professionals at Hospital da Luz and is based on the knowledge available at the time of publication or the most recent update, as indicated at the beginning of each item. English translation generated with AI and reviewed by the editorial team.
